move frame_stroke_width to makros.h
align button padding and frame size to stroke width
fix indicator positioning and padding (generic stroke introduced bug)
revisit tabs

inverted headers need no bold font to
indicate "here's the tabbar"
otoh, the bold selected header doesn't required
an additional frame corner
-> save some space

finally, document mode tabs don't even need a
bottom line, which rather adds collision with
nearby lineedits